The Rug Doctor Mighty Pro will clean approximately 118 sq ft with a full solution tank (2.6 gallons).  Detergent is available for purchase in sizes of 32 oz for $11.95, 64 oz for $19.95, or 128 oz for $29.95.  Add 2 oz of detergent per gallon of clean water.  1 oz of detergent will cover approximately 20 sq ft.